Detection of Inconsistencies Between a Reference and a Multi Format Soundtrack

ABSTRACT

Automatic detection of errors among different formatted sound tracks of the same language on a motion picture film stock can be achieved by first acquiring successive audio segments from each of the sound tracks. During a time window of prescribed duration, the audio of each different formatted track undergoes analysis to yield a numeric value. The successive analysis of the audio continues until no further audio exists for analysis. The resultant collection of numeric values undergoes formatting into a numeric file for comparison against a reference file representing audio obtained from a particular source, such as originally recorded material, a sound print, or a duplicated copy of a sound film. If the difference between a formatted numerical file and the reference file exceeds a threshold value, then an error exists in that formatted sound track, and an operator can take appropriate action.

TECHNICAL FIELD

This invention relates to checking the contents of multiple soundchannels, and in particular, to checking soundtracks on a motion picturefilm stock.

BACKGROUND OF THE INVENTION

Typically, motion picture films released for public exhibition includefour soundtracks each recorded in a different format. The four differentformat soundtracks collectively comprise a “quad” format opticalsoundtrack. The quad format advantageously allows reproduction byequipment compatible with any one of the four-recorded formats. The fourseparate audio tracks have different locations on the film. For example,the sound track for a Digital Theater System Corp. or DTS® formattedsound file lies between the edge of the film frame and the SMPTEstandardized location for a variable area audio track. (DTS® is aregistered mark of the Digital Theater System Corp.) The DTS® code trackprovides a synchronization signal for an external DTS® CD player whichcan provide six audio channels. A Dolby SR® encoded track lies in thevariable area audio track position and this signal provides backwardscompatibility for cinema sound processors incapable of signal decoding.(Dolby SR® is a registered mark of Dolby Laboratories Inc.) The DolbySR® track offers the simplest reproducing system, namely a stereoformatted audio signal, or stereo plus two additional channels. A DolbyDigital® (SR.D) track lies in the area between film perforations andsupports six channels of audio and is typically known as 5.1. A fourthrecording format developed by Sony and known as Sony Dynamic DigitalSound® or SDDS® offers eight channels of audio with data recorded at theedges of the film. (Sony Dynamic Digital Sound® and SDDS® are registeredmarks of Sony Corp.) In this way, the quad format optical soundtrackoffers enhanced playback capability that is backwardly compatible withstereo variable area (SVA) cinema sound processors.

To appreciate the composition of the quad format soundtrack, aconsideration of the original sound assembly procedures will be helpful.A typical mixing operation to create a quad format sound track combinesvarious separate sources, including dialogue, sound effects, ambiance,and music, with each originating from mono or multi-track sources. Themixing operation yields a six channel discrete sound format known as theoriginal master mix. The term discrete sound format typically means thatno relationship exists among different channels. The original master mixincludes dialogue that represents about 95% of the normal sound contentand is usually located in the center channel, sometimes 5% can belocated or combined on left and/or right or surround channels andmanipulated for effect, for example emanating from a radio, TV ortelephone. If required, an operator can add reverberation on the centerchannel alone, or occasionally on the lateral or surround channel. Soundeffects related to the dialogue, such as foot steps, etc exist with thedialogue in the center channel. Other effects can be located on thelateral or surround channels to increase the sound perspective. Specialeffects normally exist on all channels depending to the required result.Action ambiance is normally located in the lateral or surround channels.However, sometimes an operator will place the ambience in the centerchannel if such ambience exists as part of the original sound track. Ifan original music recording exists in a multi-channel format, the centerchannel will typically contain any solo instrument or vocalist. Thelateral, surround and subwoofer channels provide the main support forthe sound contents.

During mixing of various signals, audio processors can providereverberation and can add perspective by the use of delay or specialfilter functions, simulation on music or ambiance. These acousticenhancements, while fully permissible, nonetheless can introduceunexpected and undesired phase shifts, during encoding, such as by asDolby SR® encoding, and subsequently reproduced in a monaural or atwo-track stereo format.

In the digital film domain, the discrete tracks can very faithfullydeliver to the listener the original sound perspective of the mastermix. However, the various coding algorithms employed by the threedigital systems can introduce differences into the sound. For example,one encoding system includes the subwoofer channel sound content in thesurround channels, thus using just five tracks instead of six.

Mixing the original six channel master mix into a four track master mixyields an analog format audio signal comprising left, right, center andsurround channels. These four channels are processed, for example usinga Dolby SR® 4:2 spatial encoder, to form a two-track encoded audiosignal which enables stereo reproduction and, in addition, also enablesdecoding to restore the four tracks of the master mix with substantiallysimilar quality. The encoder output produces two encoded channelsidentified as Left total and Right total or Lt-Rt. These two encodedtracks pass through two Dolby SR® noise reduction processors forrecording on the optical negative film. During film exhibition, thesetwo encoded tracks are reproduced and coupled, for example, via andappropriate Dolby SR® equipped reader followed by a 2:4 decoder whichtransforms the encoded channels Lt-Rt to recreate the original fourdiscrete channels, Left, Right, Center and Surround.

Ideally, the four soundtrack formats should be substantially similar incontents, if not identical, within the constraints of each individualsystem parameters. However, manipulation of various acoustic parametersin the digitally formatted tracks can produce unwanted and unexpectedconsequences, especially when using Dolby Surround encoding anddecoding. Thus, a need exists need for a technique for rapidlyidentifying the occurrence of such unwanted acoustic consequences.

BRIEF SUMMARY OF THE INVENTION

Briefly, in accordance with a preferred embodiment of the presentprinciples, there is provided a method for automatically detectingerrors among different formatted soundtracks of the same languageversion without the need for a check by human listening. The methodcommences by acquiring contemporarily successive audio segments fromeach of a plurality of different formatted sound tracks. During a timewindow of preset duration, the audio of each different formatted trackundergoes analysis to yield a numeric value. The successive analysis ofthe audio continues until no further audio exists for analysis. Theresultant collection of numeric values undergoes formatting into anumeric file for comparison against a file representing audio obtainedfrom a particular source, such as originally recorded material, a soundprint, or a duplicated copy of a sound film. If the difference between aformatted numerical file and the comparison file exceeds a thresholdvalue, then an error exists in that formatted sound track, and anoperator can take appropriate action.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art dubbing and transfer system, which produces aquad-formatted, recorded sound track for reproduction on a motionpicture film stock;

FIG. 2 shows a typical arrangement for soundtrack reproduction from amotion picture film stock;

FIG. 3 is a block diagram showing a monitoring system in accordance witha preferred embodiment of the present principles;

FIG. 4 depicts in flow chart form the steps of a program executed by themonitoring system of FIG. 3 to automatically check sound formats; and

FIG. 5 depicts in flow chart form the steps of an analysis procedureexecuted during the program of FIG. 4.

DETAILED DESCRIPTION

FIG. 1 depicts a prior art dubbing and transfer system employed fortransferring (i.e., dubbing) audio information onto a 35 millimetermotion picture film stock 14. The system of FIG. 1 includes a DubbingStudio 10, a Digital Theater Sound Transfer Center 11 and an OpticalTransfer Center 12. The Dubbing Studio 10 receives separate audio filesfrom at least one source 16. The source 16 comprises a plurality ofdifferent audio files, including: (a) the original dialogue, (b) theoriginal music performances, (c) the original sound effects, and (d) theoriginal environmental sounds, all formatted in each of the Dolby SR®digital (SR.D), DTS® and SDDS® formats, with or without Surround EX.Within the dubbing studio 10, a mixer 18 serves to mix selected audiofiles from the source 16. Effectively, the mixer 18 includes a six trackdigital mixer 20 for mixing six tracks of SR.D files and for providingtwo tracks of analog audio in a SR format. When dubbing of foreignlanguages is necessary, the dubbing studio 11 can include a separatemixer (not shown) ahead of the mixer 18 for mixing the local dialogues.A magneto-optical (MO) disk 24 serves to store the audio mixed by themixers 20 and 22, to maintain a Dolby SR.D formatted audio file and ananalog Dolby SR file.

Within the DTS transfer center 11, a mixer 26 provides a mix of audiofiles received from the mixer 18 in the dubbing studio 10. The mixedfiles from the mixer 26 are recorded by a DTS® master recorder 28. Fromthe recording made by the DTS® recorder 28, a DTS® CD master machine 30makes a CD master for duplication by a DTS® duplicator 32. The DTS® CDwhich can provide six audio channels synchronized to the DTS sound trackon the film.

Within the optical transfer center 12, a MO disk 34 stores the DolbySR.D and analog Dolby SR sound files received from the MO disk 24. TheMO disk 34 simultaneously provides audio files to a Dolby® digitaloptical recorder 36, an analog optical recorder 38 and to a DTS® opticalrecorder 40, each recording respective formatted soundtracks on the filmstock 14. In the illustrated embodiment, the dubbing center 10 and theoptical transfer center 12 have separate MO disks 24 and 34,respectively. Rather provide a separate MO disk 34 within the opticaltransfer center 12; each of the recorders 36, 38 and 40 could directlyaccess the MO disk 24 for files. With the optical transfer center 12, amixer 42 receives the mixed files from the mixer 18 for further mixing.A SDDS® recorder 44 optically records mixed files from the mixer 44 ontothe film stock 14.

In practice, the DTS® recorder 40 records a time code track on the filmstock 14 in the region between the variable area audio track or tracksand the edge of the film frame. The recorder 38 writes a Dolby SR® trackin the standardized sound track location, while the recorder 36 writes aDolby SR Digital® track in the area between the perforations. At bothfilm edges, the recorder 44 records SDDS® tracks. The four tracksrecorded in this fashion, referred to as a quad format, provide anenhanced playback capability that is backward compatible with aconventional variable area analog sound system.

FIG. 2 depicts a block diagram of a typical prior art audio reproductionsystem 46 for use in a movie theater (cinema) for reproducing each ofthe different audio formats recorded on the film stock 14. Thereproduction system 46 of FIG. 3 includes readers 48, 50, 52, and 54,for reading the Dolby SR.D®, Dolby SR®, Sony SDDS® audio tracks, plusDTS® time code track, respectively, from the film stock 14. Each ofdecoders 56, 58 and 60 decodes its proprietary audio format receivedfrom its respective reader 48, 52 and 54. An analog equalizer 62 servesto equalize the analog Dolby SR® signal received from the reader 50.

A sound processor 64 processes receives the output signals from thedecoders 56, 58 and 62 and the analog equalizer 52 prior toamplification by an amplifier 66 that drives a set of speakers 68. Inthis way, the sound processor 64 drives reproduction of the digitallyformatted tracks in compliance with an ISO standard 2969/87 for theB-chain. The soundtrack signals originating from the optical analogreader 38 are read in accordance with the ISO standard 7831/86 for theA-chain. A sound level meter 70 measures the audio level of the soundoutput by the speakers 68 to provide feedback to the sound processor 64.Noise reduction and decoding processors (not shown) can reside betweenthe equalizer 62 and the sound processor 62 to transform the encodedDolby SR® tracks back into four channels and to provide the listeningaudience with a similar sound perspective to that produced by anoriginal 5.1 recording format reproduced from Dolby Digital® encodedtracks. However, the expansion of the two encoded tracks to yield fourtracks cannot provide the full channel separation that is achievablefrom the six discrete channels reproduced from the Dolby Digital® trackand consequently can cause ambiguities when identifying certain defects.

Despite careful efforts, the sound recording process described withrespect to FIG. 1 can introduce sound content loss as well assynchronicity and/or phase errors in the sound tracks recorded on thefilm stock 14. FIG. 3 depicts a system 100, in accordance with apreferred embodiment of the present principles for automaticallydetecting errors and audible defects in a multiple format movie soundtrack, such as the sound track on the film stock 14 of FIGS. 1 and 2.The system 100 of FIG. 3 includes an audio acquisition processor 102,typically a personal computer with an audio sound card, for executing aprogram 104 denominated as “PC SynchroCheck” in FIG. 3 for the purposeof examining the sound tracks on film stock 14.

The audio acquisition processor 102 receives the different formattedsound tracks for inspection from either the MO disk 34 within theoptical transfer center 12 of FIG. 1 or from an storage device 106 thatstores the soundtracks read from a positive print film check (notshown). The soundtracks stored in the MO 34 and those played by cinemasound systems are buffered by each one of buffers 107 ₁ and 107 ₂respectively. A switch 108 selects the output of one of the buffers 107₁ and 107 ₂ for input to a summing device (preamplifier) 110 connectedto the audio acquisition processor 102. In this way, the audioacquisition processor 102 receives the formatted soundtracks stored in aselected one of the MO disk 34 and the storage device 106.

Typically, the system 100 also includes a pair of audio monitors 112₁and 112₂, each driven by the audio acquisition processor 102 to providesound monitoring within an audio facility 113 ₁ associated with theOptical Transfer Center 12 of FIG. 1, and within a theater room 113 ₂associated with the screening of a check positive print film,respectively. The audio room 113 ₁ and the theater room 113 ₂ can alsoinclude remote control units 114 ₁ and 114 ₂, respectively, forcontrolling the execution of the PC SynchroCheck program 104 by theaudio acquisition processor 102. Each remote control unit typicallyincludes a display as well as a mouse or other type of user-actuatedinput device.

FIG. 4 depicts in flow form the steps performed by the PC SynchroCheckprogram 104 for automatically detecting errors among different formattedfilm sound tracks of the same language without the need for humanhearing. The PC SynchroCheck program 104 commences upon execution ofstep 200 of FIG. 4. During step 200, the audio acquisition processprocessor 102 of FIG. 3 acquires audio files from one of the MO disk 34of FIG. 1 or from storage device 106. The audio acquired during step 200undergoes storage in a disk 202 accessible by the audio acquisitionprocess processor 102 of FIG. 4.

Following step 200, an operator initiates a manual launch of anintegration analysis routine during step 204, whereupon audioinformation stored on the disk 202 undergoes integration duringsuccessive intervals, as indicated by box 206. The details of theintegration analysis routine performed during step 204 will becomebetter understood with respect to FIG. 5.

The integration analysis routine performed during step 204 (includingthe integration process of step 205) yields a set of numerical filesexported to a document (i.e., a file) during step 208.

During step 210, an operator initiates an analysis of the data exportedduring step 208. Such data analysis occurs during execution of the PCSynchroCheck program 104 of FIG. 3 by processing a comparison of soundtracks during step 212 and by processing a comparison of files duringstep 214. As it will be better explained hereinafter, audio trackscomparison performed during step 212 is conducted between audio levelsof paired tracks (according to the sound formats) integrated duringsuccessive time windows, typically with a duration of 20 ms each. Thefile comparisons involve comparison with values in a reference file,such those coming from the acquisition of a master audio source (MO-Diskand/or DTRS). Following processing of the sound track and filecomparisons, a display of the results occurs during step 216. Based onsuch results, a decision is made during step 218 whether the soundtrackshave an error. If an error exists (i.e., one or more of the sound tracksis no good), then the audio acquisition processor 102 of FIG. 3 outputsa report during step 220, for output on one or both of the remotecontrol devices 114 ₁ and 114 _(2,) or a similar output device, such asa display monitor or a printer (not shown). Otherwise, if no errorsexist, program execution ends during step 222.

The basis for the decision made during step 218 can be found either inthe comparison conducted between numerical levels of adequately pairedtracks in the same acquisition file, or in the comparison (always in atrack-to-track basis) against a reference acquisition file representingaudio obtained from a master (i.e., the contents stored on the MO 34 ofFIGS. 1 and 3) as well as the audio obtained from a positive check printfilm. Indeed, the same decision could involve a comparison to both theformatted file of another track, and a reference file. If eithercomparison shows a difference in value greater than a preset threshold,then a “No-Good” decision would result.

FIG. 5 depicts the steps of integration analysis routine executed by theaudio acquisition processor 102 of FIG. 3 during step 204 of FIG. 4. Theintegration analysis routine of FIG. 5 commences upon execution of astart instruction 300 during which initialization occurs. Thereafter,the audio acquisition processor 102 of FIG. 4 inputs the audio signalsstored on the disk 202 during step 304. Next, simultaneous processingoccurs for each channel (audio track), including as many as twelvechannels at once. For each channel, the audio acquisition processor 102of FIG. 4 integrates the level of the audio within a time window ofprescribed duration, typically 20 ms, during step 306. The integrationoccurs in accordance with the relationship:$L_{{eq}.T} = {{10\log}❘\left( {\frac{1}{20\quad{ms}}{\int_{0}^{20}{\frac{{Vm}^{2}(t)}{{Vo}^{2}}{\mathbb{d}t}}}} \right)}$

Following the integration performed during step 306, the results arestored during step 308 yielding in a formatted text file 310, an exampleof which is found in Table I. The top row of the table provides channelidentification, with the remaining values used for comparison purposes.TABLE 1 Identification 1 2 3 4 5 6 7 8 9 10 11 12 Nb Elements 3880 38003888 3000 3880 3080 3800 3008 3088 3000 3888 3000 Integration Value 87.245.1 83.1 85.7 84.1 83.3 85.7 84.8 90.4 89.9 92.1 92.4 85.5 53.4 83.286.1 84.3 83.7 86.3 85.0 98.7 89.7 92.4 92.2 86.8 69.9 82.7 85.1 83.483.6 86.4 84.9 98.8 90.1 92.3 92.1 85.4 78.0 83.8 86.4 84.8 83.6 85.884.6 98.4 89.3 92.3 91.8 86.4 86.4 83.2 86.3 84.3 83.3 85.7 85.1 90.698.0 92.4 92.3 86.7 89.5 83.3 85.8 83.9 83.1 86.3 84.5 90.3 98.8 92.092.2 85.8 86.8 83.3 86.1 84.1 83.4 86.0 85.3 90.8 89.7 92.3 92.3 85.185.6 83.4 85.2 83.7 83.4 86.2 85.4 90.5 98.8 92.1 92.1 86.8 45.0 83.886.4 84.6 83.0 85.8 84.3 90.7 98.8 92.5 92.1 85.8 47.0 83.3 86.1 83.852.9 5.30 84.1 89.6 90.1 91.9 92.8 86.3 68.1 83.0 86.2 84.3 53.6 86.385.1 90.6 98.0 92.5 92.2 87.1 72.0 82.9 85.6 84.8 53.6 86.3 85.3 98.890.2 91.9 92.0 84.1 81.6 82.3 85.6 83.5 83.4 86.0 85.0 90.7 09.8 92.692.2 85.2 83.1 83.1 85.8 83.3 83.4 85.6 84.1 90.4 90.0 92.2 91.7

As can now be appreciated, with a standard arrangement of channels inthe multi-format movie soundtrack film stock 14 and with signalssuitably assembled and routed by the audio acquisition processor 102 ofFIG. 3, the PC SyncroCHECK software 104 can compare data ofcorrespondent columns in the Table I to find differences caused byerrors. In detail, the PC SyncroCHECK software reads each row andcalculates differences between correspondent data. If a differencesgreater than predefined tolerance is found, the software signals andrecords relevant data of the error condition for subsequent presentationon the screen and generation of the NG Report during step 220 of FIG. 4.Each row of data is corresponds to a 20 ms widow during which the soundtrack audio undergoes integration. Thus, by knowing which integrationstep yielded bad data, it becomes possible to identify the exact footageof the film stock 14 in which the error occurred.

Once an operator launches each of the Integration Analysis andSynchroCheck procedures, each procedure occurs automatically, withoutany further intervention. In particular, each procedure operates withoutthe need for any decision making. Thus, no need exists for the operatorto listen to any of the sound tracks. In this way, the sound tracksynchronization detection process of the present principles remains freeof any subjective influence.

The foregoing describes a technique for monitoring multiple soundchannels, and in particular, for monitoring sound tracks on a motionpicture film stock, to detect errors without the need for humananalysis.

1. A method for automatically detecting errors among different formattedsound tracks of the same language, comprising the steps of: acquiringaudio from each of a plurality of different formatted sound tracks;analyzing successive audio segments of each different formatted track toyield a corresponding numeric value for that segment; formatting thesuccessive numeric values associated with each audio segment into acorresponding numeric file; comparing the numeric file against anevaluation file representing audio obtained from a particular source;and indicating an error condition when the difference between theformatted numerical file and the evaluation file exceeds a thresholdvalue.
 2. The method according to claim 1 wherein the analyzing stepcomprises further comprises the steps of: integrating an audio level ofsuccessive audio segment within a time window of a prescribed duration.3. The method according to claim 1 wherein the comparison step comprisesthe step of comparing the numeric file against an evaluation filecorresponding to a formatted numeric file associated with a differentformatted sound track.
 4. The method according to claim 1 wherein thecomparison step further comprises the step of comparing the numeric fileagainst an evaluation file corresponding to a reference filerepresenting audio obtained from a particular source.
 5. The methodaccording to claim 4 wherein the reference file is obtained from amaster source.
 6. The method according to claim 4 wherein the referencefile is obtained from a positive check print film containingmulti-formatted sound tracks.
 7. The method according to claim 1 whereinthe step of indicating a error condition further comprises the step ofgenerating a report.
 8. A method for automatically detecting errorsamong different formatted sound tracks of the same language, comprisingthe steps of: acquiring audio from each of a plurality of differentformatted sound tracks; analyzing successive audio segments of eachdifferent formatted track to yield a corresponding numeric value forthat segment; formatting the successive numeric values associated witheach audio segment into a corresponding numeric file; comparing thenumeric file against an evaluation file representing audio obtained froma different multi-formatted sound track and against a reference filerepresenting audio obtained from particular source; and indicating anerror condition when the difference between the formatted numerical fileand either of the evaluation file or the reference file exceeds athreshold value.
 9. Apparatus for automatically detecting errors amongdifferent formatted sound tracks of the same language, comprising: meansfor acquiring audio from each of a plurality of different formattedsound tracks; means for analyzing successive audio segments of eachdifferent formatted track to yield a corresponding numeric value forthat segment; means for formatting the successive numeric valuesassociated with each audio segment into a corresponding numeric file;means for comparing the numeric file against an evaluation filerepresenting audio obtained from a particular source; and means forindicating an error condition when the difference between the formattednumerical file and the evaluation file exceeds a threshold value. 10.The apparatus according to claim 9 wherein the analyzing meansintegrates an audio level of successive audio segment within a timewindow of a prescribed duration.
 11. The apparatus according to claim 9wherein the comparison means compares the numeric file against anevaluation file corresponding to a formatted numeric file associatedwith a different formatted sound track.
 12. The apparatus according toclaim 9 wherein the comparison means compares the numeric file againstan evaluation file corresponding to a reference file representing audioobtained from a particular source.
 13. The apparatus according to claim12 wherein the reference file is obtained from a master source.
 14. Themethod according to claim 12 wherein the reference file is obtained froma positive check print film containing multi-formatted sound tracks. 15.Apparatus for automatically detecting errors among different formattedsound tracks of the same language, comprising: storage means storingaudio acquired from each of a plurality of different formatted soundtracks; an audio acquisition processor for (1) analyzing successiveaudio segments of each different formatted track stored in the storagemeans to yield a corresponding numeric value for that segment, (2)formatting the successive numeric values associated with each audiosegment into a corresponding numeric file, and (3) comparing the numericfile against an evaluation file representing audio obtained from aparticular source; and means for indicating an error condition when thedifference between the formatted numerical file and the evaluation fileexceeds a threshold value.
 16. The apparatus according to claim 15wherein the audio acquisition processor integrates an audio level ofsuccessive audio segment within a time window of a prescribed duration.17. The apparatus according to claim 15 wherein the audio acquisitionprocessor compares the numeric file against an evaluation filecorresponding to a formatted numeric file associated with a differentformatted sound track.
 18. The apparatus according to claim 15 whereinthe audio acquisition processor compares the numeric file against anevaluation file corresponding to a reference file representing audioobtained from a particular source.
 19. The apparatus according to claim18 wherein the reference file is obtained from a master source.
 20. Theapparatus according to claim 18 wherein the reference file is obtainedfrom a positive check print film containing multi-formatted soundtracks.